checkov.pl

   1 #!/usr/bin/perl
   2 #
   3 # checkov.pl
   4 #
   5 # Check NASM map output for overflow
   6 #
   7 # This assumes that a section for which start != vstart, both
   8 # ranges need to be checked for overflow (true for SYSLINUX)
   9 #
  10
  11 ($in, $target) = @ARGV;
  12
  13 sub overlap($$$$) {
  14     my($s1,$e1,$s2,$e2) = @_;
  15
  16     return 1 if ( $s2 < $e1 && $e2 > $s1 );
  17     return 1 if ( $s1 < $e2 && $e1 > $s2 );
  18
  19     return 0;
  20 }
  21
  22 open(IN, '<', $in) or die "$0: Cannot open input file: $in\n";
  23
  24 $section = undef;
  25 while ( $line = <IN> ) {
  26     if ( $line =~ /^-/ ) {
  27         if ( $line =~ /^\-\-\-\- Section (\S+) / ) {
  28             $section = $1;
  29         } else {
  30             $section = undef;
  31         }
  32     } elsif ( defined($section) ) {
  33         if ( $line =~ /^length\:\s*(\S+)/ ) {
  34             $length{$section} = hex $1;
  35         } elsif ( $line =~ /^start\:\s*(\S+)/ ) {
  36             $start{$section} = hex $1;
  37         } elsif ( $line =~ /^vstart\:\s*(\S+)/ ) {
  38             $vstart{$section} = hex $1;
  39         }
  40     }
  41 }
  42 close(IN);
  43
  44 $err = 0;
  45
  46 foreach $s ( keys(%start) ) {
  47     $sstart  = $start{$s};
  48     $svstart = $vstart{$s};
  49     $send    = $sstart + $length{$s};
  50     $svend   = $svstart + $length{$s};
  51
  52     if ( $send > 0x10000 || $svend > 0x10000 ) {
  53         print STDERR "$target: 16-bit overflow on section $s\n";
  54         $err++;
  55     }
  56
  57     foreach $o ( keys(%start) ) {
  58         next if ( $s ge $o );
  59
  60         $ostart  = $start{$o};
  61         $ovstart = $vstart{$o};
  62         $oend    = $ostart + $length{$o};
  63         $ovend   = $ovstart + $length{$o};
  64
  65         if ( overlap($sstart, $send, $ostart, $oend) ||
  66              overlap($svstart, $svend, $ostart, $oend) ||
  67              overlap($sstart, $send, $ovstart, $ovend) ||
  68              overlap($svstart, $svend, $ovstart, $ovend) ) {
  69             print STDERR "$target: section $s overlaps section $o\n";
  70             $err++;
  71         }
  72     }
  73 }
  74
  75 if ( $err ) {
  76     unlink($target);
  77     exit(1);
  78 } else {
  79     exit(0);
  80 }